The non‑destructive investigation of a late antique knob bow fibula (Bügelknopffibel) from Kaiseraugst/CH using Muon Induced X‑ray Emission (MIXE)

Heritage Science

11
43
(2023)
Sayani Biswas, Isabel Megatli‑Niebel, Lilian Raselli, Ronald Simke, Thomas Elias Cocolios, Nilesh Deokar, Matthias Elender, Lars Gerchow, Herbert Hess, Rustem Khasanov, Andreas Knecht, Hubertus Luetkens, Kazuhiko Ninomiya, Angela Papa, Thomas Prokscha, Peter Reiter, Akira Sato, Nathal Severijns, Toni Shiroka, Michael Seidlitz, Stergiani Marina Vogiatzi, Chennan Wang, Frederik Wauters, Nigel Warr and Alex Amato

A knob bow fibula (Bügelknopffibel) of the Leutkirch type, which typologically belongs to the second half of the 4th and early 5th century CE, was excavated in 2018 in the Roman city of Augusta Raurica, present-day Kaiseraugst (AG, Switzerland). This was analyzed for the first time for its elemental composition by using the non-destructive technique of Muon Induced X-ray Emission (MIXE) in the continuous muon beam facility at the Paul Scherrer Institute (PSI). In the present work, the detection limit is 0.4 wt% with 
∼
1.5 hours of measurement time. The fibula was measured at six different positions, at a depth of 0.3–0.4 mm inside the material. The experimental results show that the fibula is made of bronze, containing the main elements copper (Cu), zinc (Zn), tin (Sn) and lead (Pb). The compositional similarities/differences between different parts of the fibula reveal that it was manufactured as two “workpieces”. One workpiece consists of the knob (13.0±0.6 wt% Pb), bow (11.9±0.4 wt% Pb) and foot (12.5 ± 0.9 wt% Pb). These show a higher Pb content, suggesting a cast bronze. The spiral (3.2 ± 0.2 wt% Pb), which is part of the other workpiece, has a comparatively lower Pb content, suggesting a forged bronze.

DOI
10.1186/s40494-023-00880-0
Published on
nwarr